TM 9-243
TYPES AND USES - Continued
DRILL GAGES
The twist drill and drill rod gage has a series of holes with
size and decimal equivalents stamped adjacent to each
hole. One gage measures drill sizes Nos. 1 to 60; the
other gage measures drill sizes 1/16 to 1/2 inch in 1/64
inch intervals. Drill gages determine the size of a drill
and indicate the correct size of drill to use for given tap
size. Drill number and decimal size are also shown in
this type gage. Letter size drill gages are also available.
Each drill hole is identified by a letter instead of a
number, decimal, or fraction.
MARKING GAGES
Marking gages are made of wood or steel. They consist
of a graduated beam about 8 inches long on which a
head slides. The head can be fastened at any point on
the beam with a thumbscrew. The thumbscrew presses
a brass shoe tightly against the beam and locks it firmly
in position. A steel pin or spur (1) marks the wood and
projects from the beam about 1/16 inch.
A marking gage is used to mark off guidelines parallel to
an edge, end, or surface of a piece of wood. It has a
sharp spur or pin which does the marking. A marking
gage must be adjusted by setting the head the desired
distance from the spur.
USING A THICKNESS GAGE
Thickness (feeler) gages are used in one of two ways:
as a means for determining a measure or a means for
adjusting to a definite limit. A thickness gage is used to
check piston ring gap clearance in a cylinder bore.
A long blade thickness gage is used to determine the fit
between large mating surfaces. By combining blades it
is possible to obtain a wide variation of thickness.
16-5
